Here, we report morph- and sex-specific variation in digit ratio in wild painted dragon lizards (Ctenophorus pictus).
Sex-specific differences in lizard digit ratios have been reported previously ([41], [42]; but see [43]), but morph-specific variation in digit ratio has never been examined.
Variation in digit ratio in Australian painted dragon lizards is associated with the expression of at least one morph-specific trait (the gular bib).
Although studies linking prenatal environment to variation in digit ratio do imply a role for fetal testosterone, a direct cause-and-effect relation is far from proven.
In the present study we use a lizard model system, the painted dragon (Ctenophorus pictus) to investigate causes of variation in digit ratio.
The emphasis on prenatal testosterone as the major determinant of digit ratio runs counter to the fact that variation in digit ratio among human ethnic groups is far larger than differences between the sexes [24] [26].
In their study, Kratochvíl & Flegr [50] found that when using a full-factorial model with the length of the second digit as a dependent variable and the length of the fourth digit as covariate, sex did no longer contribute to variation in digit ratio in three different human data sets [50].
Our aim is twofold: (1) to describe variation in digit ratio in relation to sex and color polymorphism in wild-caught painted dragons and (2) to investigate whether experimental elevation of prenatal testosterone modifies hatchling digit ratio in the same species.
There is thus clearly a need for more experimental studies on steroid-related variation in digit ratios.
In this study, we capitalize on variation in digit development morphology within the forelimb and between the fore- and hindlimb in bats to identify candidate genes associated with development of distinct digit morphologies.
